• Title/Summary/Keyword: Aperture Field Method

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Spatio-Angular Consistent Edit Propagation for 4D Light Field Image (4 차원 Light Field 영상에서의 일관된 각도-공간적 편집 전파)

  • Williem, Williem;Park, In Kyu
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2015.11a
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    • pp.180-181
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    • 2015
  • In this paper, we present a consistent and efficient edit propagation method that is applied for light field data. Unlike conventional sparse edit propagation, the coherency between light field sub-aperture images is fully considered by utilizing light field consistency in the optimization framework. Instead of directly solving the optimization function on all light field sub-aperture images, the proposed optimization framework performs sparse edit propagation in the extended focus image domain. The extended focus image is the representative image that contains implicit depth information and the well-focused region of all sub-aperture images. The edit results in the extended focus image are then propagated back to each light field sub-aperture image. Experimental results on test images captured by a Lytro off-the-shelf light field camera confirm that the proposed method provides robust and consistent results of edited light field sub-aperture images.

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Design of a C-shaped nano-aperture in the Ag film (은 필름에서의 C형 나노 개구 설계)

  • Park, Sin-Jeung;Hahn, Jae-Won
    • 정보저장시스템학회:학술대회논문집
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    • 2005.10a
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    • pp.38-39
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    • 2005
  • A new C-aperture is needed in the Ag film because general metal films don't alternate with the PEC film. In this paper, using FDTD method and the Drude-Lorentz metal model, a new C-aperture is designed in the Ag film and the 40nm-beam size and the $7\%$ near-field transmission efficiency are obtained at 28nm distance from the aperture. Its near-field transmission is about 1000 times larger than that of a 54 nm${\times}$54 nm square aperture.

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EDUCATION OF ELECTROMAGNETIC PENETRATION THROUGH NARROW SLOTS IN CONDUCTING SCREEN BY PARALLEL PLATE LOADING (평행평판 장하에 의한 슬릿 침투 전자파의 저감 특성)

  • Park, Eun-Jung;Ju, Chang-Hyun;Kim, Ki-Chai
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2005.05a
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    • pp.66-68
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    • 2005
  • This paper presents the reduction characteristics of penetrated electromagnetic fields through a narrow slot aperture in a planar conducting screen of infinite extent. When a plane wave is excited to the narrow slot, the aperture electric field is controlled by the parallel plate connected on the slot. The magnitude of penetrated electromagnetic fields through a narrow slot is controlled by electric field distributions on the slot aperture. An integral equation for the aperture electric field on narrow slots is derived and solved by applying Galerkin's method of moments. The results show that the magnitude of the penetrated electromagnetic field can be effectively reduced by installing the parallel plate on the slot aperture.

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Aperture Cut-off Filter for Reduction of Electromagnetic Field Penetration through a Slot in Conducting Screens (도체평판의 슬롯 침투 전자파 저감을 위한 개구면 차단필터)

  • Kim, Ki-Chai
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.12
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    • pp.1201-1211
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    • 2014
  • The purpose of this paper is to present the aperture cut-off filter for reduction of electromagnetic field penetration through a slot in conducting screen. The reduction characteristics of electric field penetration by the aperture cut-off filter are considered. In order to establish the concept of the aperture cut-off filter, the integral equation on the slot aperture field distribution is derived and solved by method of moments, and the reduction characteristics of penetration electric fields for the incident plane wave are calculated. The numerical results showed that the aperture cut-off filter for reduction of electric field penetration through the slot can be realized. To check the validity of the concept of an aperture cut-off filter and the theoretical analysis, the calculated electric field penetration of the metallic wall with narrow slot were compared with the experimental results.

Measurement Guideline of Fresnel-Field Antenna Measurement Method

  • Oh, Soon-Soo;Moon, Jung-Ick
    • ETRI Journal
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    • v.31 no.1
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    • pp.68-70
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    • 2009
  • In this letter, a parametric analysis of the Fresnel-field antenna measurement method is performed for a square aperture. As a result, the optimum number of Fresnel fields for one far-field point is guided as $M_{opt}=N_{opt}=D^2/{\lambda}R+5$, where D is the antenna diameter, ${\lambda}$ is the wavelength, and R is the distance between the source antenna and the antenna under test. For the aperture size 5 ${\leq}$ $L_x/{\lambda}$ ${\leq}$ 20, the tolerable distances for gain errors of 0.5 dB and 0.2 dB can be guided as $R_{0.5\;dB}$ ${\approx}$ $1.2Lx/{\lambda}$ and $R_{0.2\;dB}$ ${\approx}$ $2.0L_x/{\lambda}$, where $L_x$ is the lateral length of the square aperture. The tolerable distances for 20 ${\leq}$ $L_x/{\lambda}$ ${\leq}$ 200 are also proposed. This measurement guideline can be fully utilized when performing the Fresnel-field antenna measurement method.

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MCNP-polimi simulation for the compressed-sensing based reconstruction in a coded-aperture imaging CAI extended to partially-coded field-of-view

  • Jeong, Manhee;Kim, Geehyun
    • Nuclear Engineering and Technology
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    • v.53 no.1
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    • pp.199-207
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    • 2021
  • This paper deals with accurate image reconstruction of gamma camera using a coded-aperture mask based on pixel-type CsI(Tl) scintillator coupled with silicon photomultipliers (SiPMs) array. Coded-aperture imaging (CAI) system typically has a smaller effective viewing angle than Compton camera. Thus, if the position of the gamma source to be searched is out of the fully-coded field-of-view (FCFOV) region of the CAI system, artifacts can be generated when the image is reconstructed by using the conventional cross-correlation (CC) method. In this work, we propose an effective method for more accurate reconstruction in CAI considering the source distribution of partially-coded field-of-view (PCFOV) in the reconstruction in attempt to overcome this drawback. We employed an iterative algorithm based on compressed-sensing (CS) and compared the reconstruction quality with that of the CC algorithm. Both algorithms were implemented and performed a systematic Monte Carlo simulation to demonstrate the possiblilty of the proposed method. The reconstructed image qualities were quantitatively evaluated in sense of the root mean square error (RMSE) and the peak signal-to-noise ratio (PSNR). Our simulation results indicate that the proposed method provides more accurate location information of the simulated gamma source than the CC-based method.

Forced Resonant Type Cutoff Cavity-Backed Aperture Antennas Loaded with a Single External Reactance

  • Kim Ki-Chai;Hirasawa Kazuhiro
    • Journal of electromagnetic engineering and science
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    • v.5 no.3
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    • pp.105-111
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    • 2005
  • This paper presents the basic characteristics of a cutoff cavity-backed aperture antenna with a feed post and a parasitic post inserted parallel to the aperture. It is shown that this type of antenna forcibly resonates the cutoff cavity by adding a single external reactance to the parasitic post. The Galerkin's method of moments is used to analyze integral equations for the unknown electric current on each post and the aperture electric field on the aperture. The value of an external reactance for forced resonance is analytically obtained by deriving a determining equation. Also the current distribution on each post, aperture electric field distributions, and the radiation patterns are discussed. The theoretical analysis is verified by the measured return loss and radiation patterns.

Developing a Cantilever-type Near-field Scanning Optical Microscope Using a Single Laser for Topography Detection and Sample Excitation

  • Ng'ang'a, Douglas Kagoiya;Ali, Luqman;Lee, Yong Joong;Byeon, Clare Chisu
    • Current Optics and Photonics
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    • v.5 no.3
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    • pp.229-237
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    • 2021
  • The capabilities of the near-field scanning optical microscope (NSOM) for obtaining high resolution lateral topographical images as well as for mapping the spectroscopic and optical properties of a sample below the diffraction limit of light have made it an attractive research field for most researchers dealing with optical characteristics of materials in nano scales. The apertured NSOM technique involves confining light into an aperture of sub-wavelength size and using it to illuminate a sample maintained at a distance equal to a fraction of the sub-wavelength aperture (near-field region). In this article, we present a setup for developing NSOM using a cantilever with a sub-wavelength aperture at the tip. A single laser is used for both cantilever deflection measurement and near-field sample excitation. The laser beam is focused at the apex of the cantilever where a portion of the beam is reflected and the other portion goes through the aperture and causes local near-field optical excitation of the sample, which is then raster scanned in the near-field region. The reflected beam is used for an optical beam deflection technique that yields topographical images by controlling the probe-sample in nano-distance. The fluorescence emissions signal is detected in far-field by the help of a silicon avalanche photodiode. The images obtained using this method show a good correlation between the topographical image and the mapping of the fluorescence emissions.

Analysis of Axially Displaced Ellipse Gregorian Dual Reflector Antennas (축이동 그레고리안 이중 반사경 안테나의 해석)

  • 임성빈;최경국;최학근
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.11
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    • pp.1161-1169
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    • 2003
  • In this paper, ADE(Axially Displaced Ellipse) Gregorian dual reflector antennas, which are the special form of Gregorian dual reflector antennas, were analyzed. In the procedure of antenna analysis, the aperture field distribution was obtained by using the geometrical optics and their far-field radiation characteristics were analyzed by using the aperture field method. The analysis results such as antenna efficiency, HPBW(Half Power Beam Width), FNBW(First Null Beam Width), and FSL(First Sidelobe Level) were presented as functions of edge taper and size of main reflector and subreflector. From the results in this paper, we could confirm that ADE reflector antennas have the different radiation characteristics from the classical dual reflector antennas.

GTD Analysis of Electromagnetic Plane Wave Scattering by Open-Ended Parallel Plate Waveguide with a Slanted Terminator Inside (GTD를 이용한 경사진 벽으로 막힌 평행도파관의 전자파 산란 해석)

  • 선영식;명노훈
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.29A no.11
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    • pp.19-24
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    • 1992
  • In this paper, a high frequency method is developed which combines the uniform Geometrical Theory of Diffraction(GTD) and the Aperture Integration(AI) to analyze electromagnetic plane wave scattering by a perfectly-conducting, open-ended, semi-infinite parallel plate waveguide with a uniform layer of absorbing material on its inner wall, and with a slanted planar termination inside. In this method, first, the field of an arbitary point inside the paraller plate waveguide is computed by the GTD. Second, the field scattered into exterior region by the waveguide is found using the equivalent current, which can be obtaind from the aperture field of the waveguide and using the AI. Numerical results based on this GTD method are presented and compared with those based on the mode matching method.

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